The invention relates generally to a method of preparing a package, and specifically to a method of preparing a package having a multiple-film lid. The multiple-film lid has an impermeable film which may be peeled so as to expose a permeable film.
Present methods for packaging products such as fresh red meats and the like involve evacuating and gas flushing the interior spaces of the package so as to enhance the shelf-life and appearance of the product contained in the package.
A problem encountered particularly with respect to packaging of fresh red meats is that removal of oxygen in an evacuated package causes the meat to take on a purplish color which is not desirable to consumers. Responsive to this problem, packages have been developed which include an oxygen-permeable or non-barrier film enclosing the product, and a peelable oxygen barrier or impermeable film disposed over the permeable film. Generally as used herein, the term "impermeable" connotes gas impermeability as further described and defined below. This type of package provides the advantage that the interior space of the package can be evacuated and back-flushed with low oxygen gas or gases for shipping and long-term storage and, when the product is to be displayed for the consumer, the impermeable film is removed to allow atmospheric oxygen to permeate the permeable film and thereby cause the fresh red meat product to "bloom" or take on a bright red color which the consumer associates with freshness.
A problem encountered with the preparation of packages having permeable and impermeable films is that residual air or gas containing oxygen is frequently trapped in the space between the films. This occurs because it is difficult to pull a vacuum between the permeable and impermeable films without disrupting the permeable lid, leading to trapped residual gas or air which can allow oxygen to permeate the permeable film, expose the product prematurely to oxygen, and damage the product.
One approach designed to avoid the problem of trapped residual gas is to apply the permeable film and impermeable film layer at separate sealing/evacuation stations. Although this approach may reduce the problem of trapped residual gas and air, a disadvantage remains in that two sealing/evacuation stations must now be used. This can create a number of problems. Second stage evacuation can damage or distend the permeable film. Also, the two-step operation can decrease manufacturing efficiency. Moreover, the extra stage requires increased space for the packaging apparatus.
Accordingly, there is a need in the art for an improved method of preparing a package having a multiple-film lid, including a permeable film and an impermeable film, wherein both films are sealed at a single sealing station. Such a method would desirably provide evacuation between the permeable film and the impermeable film, thereby avoiding the aforementioned problems associated with trapped air between the films.